Epigenetics, DNA Methylation, and Their Role in Cancer

Abstract

Epigenetics refers to changes of gene expression that do not affect changes in the nucleotide sequence. One mechanism of epigenetic modification is DNA methylation. DNA methylation is an important process of normal development in organisms; specifically it is an integral part of cell differentiation, and is thus is different between different species, organs, and tissues. DNA methylation involves the addition of a methyl group to DNA (Vanyushin, B.F., Mazin, A.L., Vasiliev, V.K., and Beloz- ersky, A.N., 1973). Specifically, the methyl group is either added to cytosine (or sometimes adenine) bases. With the addition of a methyl group, cytosine is converted to 5-methylcytosine and adenine is converted to N6-methyladenine. DNA methylation occurs often in repeated DNA sequences. DNA methylation can modify the structure, and thus the function, of proteins in the body (Vanyushin, B.F., 1973). The modifications can affect all processes05in the cells. Hypermethylation often leads to suppressed expression. It has been shown that maligant cells have irregular patterns of DNA methylation; therefore, disruption in these patterns has been used to diagnose carcinogenesis (Shif, M., 2005). DNA methylation is now being intensely studied, due to its potential role in tumorigenesis (Kulis, M., Esteller, M, 2010). Also, although epigenetic changes do not change the DNA sequence of an organism, recent research has shown that these alterations persist through cell divisions and may be heritable and may be passed down to offspring.